431 



condition being about as described by Heidenreich. But even here 

 when the nodes and the internodal segments of the contraction areas 

 are compared with the entii-ely relaxed muscle (Figs. 1 and 2) it will 

 be seen clearly that though in contracted muscle the nodes often have 

 a smaller caliber than the internodal segments, yet the nodes have a 

 larger caliber than in the relaxed muscle fiber. Furthermore, from 

 the shortening of the nuclei and the condensation of the connective 

 tissue, it will be seen that the fibrillated internodal segments have 

 also undergone some contraction. That they should still be larger in 

 cross section than the more firmly contracted nodes is somewhat diffi- 

 cult to understand. Heiden- 

 reich's idea that it is due 

 to shrinkage does not harmo- | 

 nize with what is found in the 

 dog (Fig. 5), where thej nodes -^ 

 are uniformly of larger caliber 

 than the internodal segments. 



Fig. 4. 



Fig. 5. 



Fig. 4. Intestine of Necturus, showing contraction nodes and :i portion of an un- 

 contracted fiber with a spiral nucleus, a spiral nucleus; b contraction node, c inter- 

 nodal segment; d anastomosis between two smooth muscle fibers. Fixation, Zenker's 

 fluid; stain, iron-htematoxylin. Zeiss apochrom. oV)]. 2 mm, comp. oc. 8, drawing re- 

 duced ^/g, magnification, 800 diameters. 



Fig. 5. Large intestine of dog from a contraction area. a contraction node; 

 b intemodal segment; c condensed connective tissue; d loose connective tissue. Fixation, 

 Zenker's fluid ; stain, iron - hiematoxylin. Leitz obj. 7, oc. 2 , drawing reduced Yg, 

 magnification, 352 diameters. 



In all of the material studied, the muscle nuclei in the contraction 

 waves are closer together and much shorter and thicker than in the 

 uncontracted muscle. The elongated relaxed nuclei shown in Fig. 1 

 may be contrasted with the short contracted nuclei in Fig. 2. The 

 nucleus in contracted muscle undergoes a distinct decrease in length 



